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Title: An optimal direct synthesis of CrSBA-15 mesoporous materials with enhanced hydrothermal stability
Authors: Selvaraj, M.
Kawi, S. 
Issue Date: 6-Feb-2007
Citation: Selvaraj, M., Kawi, S. (2007-02-06). An optimal direct synthesis of CrSBA-15 mesoporous materials with enhanced hydrothermal stability. Chemistry of Materials 19 (3) : 509-519. ScholarBank@NUS Repository.
Abstract: Mesoporous CrSBA-15 materials with different nsinCr ratios have been synthesized, for the first time, using Pluronic P123 as a structure-directing agent by simply adjusting the molar ratio of water to hydrochloric acid (nH2O/nHCl). The effect of the nature of Cr-ion source on the synthesis of CrSBA-15 has been investigated using different chromium-ion sources: chromium(III) nitrate, chromium(III) chloride, and chromium(III) sulfate. To investigate the effect of structural and textural properties with a higher Cr incorporation, CrSBA-15 has also been synthesized with various nSi/nCr ratios and synthesis temperatures. The synthesized CrSBA-15 materials have been characterized by ICP-AES, XRD, N2 adsorption, ESR, TEM, and FE-SEM. ICP-AES results show that chromium(III) nitrate nonohydrate is found to be a good Cr-ion source for the synthesis of mesoporous CrSBA-15 material, with a nSi/nCr ratio up to 9.1 successfully prepared by changing the nSi/n Cr ratio in the synthesis gel at a nH2O/nHCl of 295. For all calcined CrSBA-15 materials, XRD reflection peaks shift to lower angle with increasing Cr-content, resulting in the increase of the unit cell parameter. By increasing the crystallization temperature from 373 to 403 K, nitrogen adsorption measurement shows that the pore diameter of CrSBA-15 can be tuned from 89.4 to 94.7 Å, with an increase of pore volume from 1.10 to 1.20 cm3/g accompanied by the concomitant decrease of surface area from 987 to 797 m2/g and the decrease of pore wall thickness from 38 to 36.7 A. ESR measurements show the amount of Cr-ions incorporated, as well as the location and coordination of Cr-ion on SB A-15 silica walls. TEM and FE-SEM images show the uniform pore diameter and ropelike hexagonal mesoporous structure of CrSBA-15. Furthermore, the hydrothermal stability of CrSBA-15 samples has also been investigated, with hexagonal CrSB A-15(8) having better hydrothermal stability than CrSBA-15(50). © 2007 American Chemical Society.
Source Title: Chemistry of Materials
ISSN: 08974756
DOI: 10.1021/cm062009r
Appears in Collections:Staff Publications

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